Ballistics - Heavy Bullets

A Long Range Competitor Looks at Heavy Bullets
by Germán A. Salazar
This article first appeared in May of 2008 at www.accurateshooter.com

A number of years ago I read an article by Dr. Geoff Kolbe, founder and owner of Border Barrels in Scotland titled “Comments on Long Range Ballistics”. Dr. Kolbe’s straightforward assertion in that article was that there is no such thing as a bullet which is too heavy for long-range (prone) shooting. This position runs counter to the widely held belief that there is a “tipping point” at which the muzzle velocity reduction caused by the heavier bullet will cause it to drift more than a lighter bullet with a higher MV. Dr. Kolbe, demonstrated in that article, that for a given cartridge (he used the .308) as long as each bullet is of similar form and is loaded to the same pressure, with a suitable powder, then the heavier (higher BC) bullet will always drift less, regardless of MV.


Heavy Bullets Work
That article made me a heavy bullet shooter and for many years my long-range rifle was a Model 70 in 30-06 with a 1:8" twist Krieger barrel shooting the 240 Sierra MK. While the recoil wasn’t for the casual shooter or for the 17 lb. AR15 types, it was very manageable and produced many match winning scores. Being somewhat experimentally minded, other projects called and the heavy bullet 30-06 fell into disuse a few years ago. More recently I’ve continued along the heavy bullet path by using the Berger 115 grain 6mm bullet in a 6XC and again, it has proven to be an excellent combination; most recently winning the 2008 Arizona Long Range State Championship with a 797-42X at 1000 yards. Whatever the caliber, heavy bullets work.

Berger Bullets has recently developed a new line of non-VLD, standard profile match bullets in various calibers. I felt this was a good opportunity to put Dr. Kolbe’s theory to the test, since Bob Jensen and I have been doing a large amount of pressure/velocity testing lately with the 30-06 in support of another project. Berger’s new line includes 175 grain, 185 grain and 210 grain bullets in .30 caliber, a perfect selection for our project. A new 30” long, 1:10" twist Bartlein barrel was fitted and chambered by Clark Fay of Raton, New Mexico and we were back in business. I should note that this barrel has a perfectly standard 30-06 chamber, no special throating for heavy bullets, although that may come later.


Reaching Max Pressure
After sorting through loads with a few powders, we determined that Hodgdon’s H4350 would produce maximum pressure levels (60,000 psi) at appropriate velocities for the three Berger bullets and a few others we brought along for comparison. We also tried H4831sc but we were unable to reach maximum pressure before reaching the limits of the 30-06 case’s capacity. There may be other powders that can accomplish the pressure/velocity combination we need, but H4350 is a well proven powder in the 30-06 and made a good choice. We used an Oehler 43 Personal Ballistics Lab with the appropriate strain gauge on the barrel to measure pressure and velocity. All bullets used in this test were moly-coated with the NECO process.

Below is a chart showing the six bullets tested, the muzzle velocity attained with each one at 60,000 psi chamber pressure, remaining velocity at 1000 yards and wind drift calculations at 1000 yards. Remaining velocity and drift are calculated using each manufacturer’s advertised ballistic coefficient. While this may not provide a perfect comparison across brands, it is certainly a valid method for brand specific comparisons are the same methodology is used to calculate each brand’s BC.





SEE TABLE AT BOTTOM

Kolbe Was Right!
Even a passing glance at this table will show that Dr. Kolbe was right on the money – no surprise there. The three Berger bullets are of the same form as each other and the two Sierra bullets are of the same form as each other and each brand’s BC methodology is internally consistent. The MV shown for each bullet is the highest that we could reach within the 60,000 psi SAAMI limit for the 30-06. Clearly, there are bullet design issues such as bearing surface length which affect pressure to a greater degree than even bullet weight.

As muzzle velocity increases, drag on the bullet increases disproportionately; thus, most of what you gain in MV is quickly lost. Note that the heavier bullets (in each type) had a higher remaining velocity at 1000 yards despite starting out slower. Muzzle velocity, like a new car, is a depreciating asset, but BC, like diamonds, is forever.

Should you immediately run out to buy the heaviest bullets available for your caliber of rifle? Not necessarily; we haven’t spoken about accuracy, recoil or chamber and twist rate suitability for heavier bullets, all of which must be taken into consideration. However, hopefully you now have a better understanding of the result of bullet choices and are in a position to make a more fully informed decision for your next cartridge/barrel/bullet selection.























Bullet





Muzzle Velocity (fps)





Velocity at 1000 Yd. (fps)





Drift at 1000 Yd. (inches)





Berger 210





2730





1611





59.2





Berger 185





2900





1605





63.6





Berger 175





2980





1593





66.2





Lapua 185 D46





2880





1548





67.9





Sierra 200 MK





2760





1498





69.7





Sierra 190 MK





2820





1472





73.0
 

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